Freezer with inner core

ABSTRACT

The frozen dessert machine of the present invention provides an inner core in its refrigeration chamber.

BACKGROUND OF THE INVENTION

The present invention relates to freezers, and, in particular, to afreezer for making frozen desserts. This invention is related to threeother concurrently-filed applications, entitled "FREEZER WITH GROOVEDHEAT EXCHANGE SURFACE", "AERATOR FOR VISCOUS MATERIALS", and "DISPENSERFOR SOFT-SERVE FROZEN DESSERT MACHINE".

Frozen dessert machines include a freezing chamber and a dasher insidethe freezing chamber for mixing the frozen dessert and scraping it fromthe surface of the freezer. The frozen dessert is dispensed from thefront of the freezing chamber. In prior art soft-serve machines, thedrive shaft for driving the dasher enters the back of the freezer, andthe dasher connects to the drive shaft at the back of the freezer. Thefrozen dessert enters the freezer at the back and then moves to thefront of the freezer to be dispensed out the front. There is a sealbetween the freezer and the drive shaft to prevent the liquid mix frommaking its way out of the freezer along the driveshaft. It is verycommon for that seal between the drive shaft and the freezer to leak, soliquid mix does make its way out of the freezer and falls somewhere inthe back of the machine. That liquid mix then sits in the machine for anextended period of time, spoiling, attracting pests, and generallypresenting an undesirable situation.

The freezer arrangement with the seal in the back of the machine alsoincludes many nooks and crannies in the mechanism in which the productcan accumulate. For that reason, health rules require the entire freezerto be taken apart piece by piece, washed, and reassembled every day.This is a very labor-intensive process. Also, since it does require somuch work, some facilities do not do the required daily washing, therebyrisking the health of their customers.

SUMMARY OF THE INVENTION

The present invention overcomes the problems of the prior art bysubstantially changing the design of the freezer.

The present invention has a freezer with an inner core, permitting thedriveshaft to extend through the inner core of the freezer so theconnection between the driveshaft and dasher can be made at the front ofthe machine.

The present invention eliminates the nooks and crannies which requiredthe machine to be disassembled for cleaning and permits the machine tobe cleaned in place, greatly reducing labor costs.

The present invention puts the seal at the front of the machine, whereit can be inspected frequently and where it can easily be replaced by anoperator, without requiring a service call.

The fact that there is a core in the center of the freezing chamberreduces the distance from the heat transfer surface to the product,which permits the freezer to freeze the entire product more quickly.

The present invention has no seals at the back of the freezer to permitleaking or to provide nooks and crannies for product to accumulate.

It is possible to create an additional heat exchange surface at thecore, so that the frozen dessert can be chilled from both the outer heatexchange surface and the inner heat exchange surface.

The present invention provides a seal at the front of the machine whichis very easy to replace.

The present invention provides a tube for directing any leaked materialto the front of the machine so the operator can detect very quicklywhether there is a leak in the seal.

The present invention provides a drive shaft portion which is easilyremovable from the machine so that, in the event of a leak, the innercore can readily be cleaned out.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the front of the frozen dessertmachine of the present invention;

FIG. 2 is a schematic view taken along the section 2--2 of FIG. 1;

FIG. 3 is a schematic view taken along the section 3--3 of FIG. 1;

FIG. 4 is a perspective view of the mixing chamber of the machine ofFIG. 1;

FIG. 5 is an enlarged perspective view of some of the spiral blades ofthe mixing chamber of FIG. 4;

FIG. 6 is a right side sectional view of the freezing chamber of FIG. 2;

FIG. 7 is a view taken along the section 7--7 of FIG. 6;

FIG. 8 is a perspective view of the dasher portion of the freezer ofFIG. 6;

FIG. 9 is a top view of the dispenser portion of the machine of FIG. 1;

FIG. 10 is a front view of the dispenser portion of the machine of FIG.1 partially in section;

FIG. 11 is a schematic diagram of the dispenser control;

FIG. 12 shows a side sectional view of the freezer in a secondembodiment of the invention in which refrigerant also circulates in theinner core of the freezing chamber;

FIG. 13 is an enlarged perspective view of the boxes of liquid mix shownin FIG. 3; and

FIG. 14 is a broken-away, enlarged view of a portion of the front of themachine of FIG. 1, showing the control buttons on the left side of themachine.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the outside of the soft-serve frozen dessert machine 10,which includes an outer shell 12 and which rides on casters 14. Near thebottom of the shell 12 are vent openings 16, which permit air to flowthrough the bottom portion of the machine 10. In the front of themachine 10 are three dispensing nozzles 18, 20, 22. The nozzle 18 on theleft dispenses frozen dessert from the left freezing chamber (shown inlater figures), the nozzle 22 on the right dispenses frozen dessert fromthe right freezing chamber, and the nozzle 20 in the middle dispenses amixture of the frozen desserts from both the left and right freezingchambers.

Above each dispenser 18, 20, 22 are four buttons 24 for selecting thevarious and adjustable portion sizes to be dispensed from eachdispenser. One set of these buttons is shown more clearly in FIG. 14.There is also another set of buttons 25 on the left and right sides ofthe machine for controlling the operation of the machine for cleaningand maintenance. These buttons 25 are also shown more clearly in FIG.14. Below the dispensers 18, 20, 22 is a tray 26, on which the machineoperator can place cups, cones, or other containers for receiving thedessert from the dispensers. Below the tray 26 is a door 28, which opensinto a refrigerated compartment, which will be described later. Thelower portion of the refrigerator door 28 opens into an unrefrigeratedcompartment which houses bottled air (of course, any suitable bottledgas could be used), as will be described later. It should be noted thatthis machine 10 includes two soft-serve frozen dessert freezers, one onthe left side and one on the right side, and the left and right sides ofthe machine are essentially mirror images of each other.

Looking now at FIG. 2, again we can see the outer shell 12, thedispenser 22, the tray 26, the buttons 24, and the refrigerator door 28.We can also now see the inside of the machine 10. The major componentsare as follows:

Near the top of the machine 10 are two freezing chambers 32. In thisview, we see the right freezing chamber 32, which is aligned with theright dispenser 22. Behind each freezing chamber 32 is a gear drive 34,which is driven by an electric motor 36. Below the two freezing chambers32 is a single refrigerated chamber 38, which extends across the entirewidth of the machine 10 and lies directly behind the door 28, which wasshown in FIG. 1. Inside the refrigerated chamber 38 is an evaporator 37through which coolant passes to cool the refrigerated chamber 38. Aplurality of boxes 40 of liquid frozen dessert mix are located in therefrigerated chamber 38. When the frozen dessert mix is aerated andchilled, it will become the final frozen dessert product. This is bestseen in FIGS. 3 and 13, illustrating the use of four boxes 40. The twoboxes on the left feed the left freezer, and the two boxes on the rightfeed the right freezer. There is a switching valve 41 for each pair ofboxes 40. The switching valves 41 sense when a vacuum is being pulled ina box 40, indicating that the box is empty, and then automaticallyswitch over to the other box 40, at the same time turning on the "AddMix/Low Product" light on the control panel 25. When the operatorreplaces the empty box 40, the operator also pushes the "Reset" buttonto turn off that light. In the back portion of the refrigerated chamber38 are two mixing chambers 42, where the liquid mix 40 is mixed with air(or other gas), as will be described in detail later. Below therefrigerated chamber are two bottles 44 of medical-grade bottled gas.Both freezers 32 operate off of a single bottle of gas 44 at any giventime, and a light on the control panel 25 indicates when the pressure inthe bottle 44 is low so that an operator must switch the machine over tothe other bottle 44, put in a fresh bottle 44 which is pressurecontrolled and which automatically resets the light on the control panel25, thereby permitting continuous operation. We can see the right bottle44 in FIG. 2. Behind the refrigerated chamber 38 are a number ofsolenoid valves 46, which control the flow of fluids in the machine 10.Below the refrigerated chamber 38 are two compressors. The largecompressor 52 runs the refrigeration unit, which provides refrigerant tothe freezers 32 and to the refrigerated chamber 38. The small compressor50 compresses ambient air and provides it as a working fluid to drivethe air-actuated dispensers 18, 20, 22.

There are several different fluid systems within the machine 10:

THE FROZEN DESSERT SYSTEM

First, there is the frozen dessert system, which begins as a liquid inits respective mix box 40. Each box 40 is connected to an asepticconnector and valve 60, which connects by an individual tube to aswitching valve 41. The liquid mix passes through the aseptic valving41, 60 and the corresponding tubing. It is then pumped by its respectivepump 62, which is driven by its respective motor 64. It is then aeratedin its respective mixing chamber 42, as will be described in more detaillater. Next, it is frozen in its respective freezer 32. Finally it isdispensed through its respective dispenser 18, 20, or 22. Any part ofthe machine which comes in contact with the frozen dessert system isfood grade material. The seals which contact the frozen dessert systemare food grade seals, and every part of the machine which comes intocontact with the frozen dessert system is free of cracks or creviceswhere bacteria could grow and is designed to be cleaned in place. Allparts of the machine which contact the frozen dessert from the pump 62up to the freezer 32 are sloped toward the pump 62 to facilitatecleaning in place.

THE PURE GAS SYSTEM

Second, there is the pure gas system. The pure gas is a dry, filtered,food grade gas, free of bacteria and other pathogens. The pure air (orother suitable gas) begins in the bottles 44, passes through a pressureregulator 45 and a flow meter with a needle valve 47, then through someof the solenoid valves 46, which direct it to the mixing chambers 42,where it is used to aerate the frozen dessert mix in the mixing chambers42. The solenoid valves 46, controlled by the central processor 186,open the flow of pure gas to the mixing chamber 42 when the pump 62 isrunning and close off the flow of gas to the mixing chamber 42 when thepump 62 is off. The mixed pure gas/frozen dessert mix is chilled in therespective freezers 32, and is dispensed out of the freezers 32 throughthe dispensers 18, 20, or 22. The solenoid valves are constructed offood grade material with bubble tight sealing. In addition, all pipingand fittings which come into contact with the pure gas are food gradematerial.

THE REFRIGERANT SYSTEM

Third, there is a refrigerant loop which is used to chill the freezers32 and the refrigerated chamber 38. The refrigerant also is used toprevent the product from freezing at the inlet of the freezer 32, toavoid plugging of product inlet, as will be described later. In thepreferred embodiment, the refrigerant is HP62. Beginning at thecompressor/condenser unit 52, the warm liquid refrigerant flows to thethawing chambers surrounding the product inlets of the freezers 32(which will be described later), and then, as is well-known in therefrigerant industry, through a filter/drier (not shown), through one ofthe solenoid valves 46, and through an expansion valve (not shown). Whenthe pressure of the refrigerant is reduced as it passes through theexpansion valve, the refrigerant temperature drops. The refrigerant thengoes through the evaporators of the freezers 32 and of the refrigeratedchamber 38, passes through a heat exchanger to vaporize any remainingliquid refrigerant, and then goes back to the compressor/condenser 52 tobegin the cycle again. As best seen in FIG. 3, fans 56 are locatedadjacent to the large compressor 52 to exhaust hot air from thecompressor/condenser 52 and to bring in cool air.

THE CONTROL AIR SYSTEM

Fourth, there is a control air system, in which ambient air iscompressed by the small compressor 50, is stored in the small air tank58, and passes through the solenoid valves 46, which control and directthe control air flow to the dispensers 18, 20, 22. The solenoid valves46, which control the flow of working fluid to the dispensers, determinewhen and for how long the dispenser valves will open. The solenoidvalves 46 are controlled by the central processor, which will bedescribed in more detail later.

Referring again to FIG. 3, we can see the left and right freezers 32 atthe top of the machine 10. Below them is the refrigerated chamber 38,which holds four boxes of liquid mix 40 and two mixing chambers 42,which lie at the back of the refrigerated chamber 38. Below therefrigerated chamber 38 are the left and right bottles of pure bottledgas 44. Below the bottles of pure gas 44 are the compressor/condenser52, the fans 56, and the small compressor 50 for providing the controlair.

FIG. 4 shows one of the mixing chambers 42 in more detail. The mixingchamber 42 is where the gas and liquid are mixed together beforeentering the freezer. The mixing chamber 42 is preferably made out oftwo pieces of molded plastic 66, which, when bonded together, form atube 68. The tube 68 is designed so that it is always inclined downward,toward the pump 62 mounted at the bottom of the mixing chamber 42. Themixing chamber 42 is made with no crevices or areas to trap product, sothat it can be cleaned in place. The tube 68 has a small-diameterportion 70, near the bottom. At the top of the tube 68 is aninternally-threaded opening 72, which permits the mixing chamber tube 68to be connected to additional tubing to transport the frozen dessert mixto the freezer 32. At the bottom of the mixing chamber tube 68 isanother internally-threaded opening 74, which permits the mixing chambertube 68 to be connected to additional tubing 76 coming from the pump 62.At the small diameter portion 70, is a gas inlet opening 78 in the backof the mixing chamber, which is also internally threaded and whichreceives the pressurized pure gas from one of the gas bottles 44 throughthe tube 80. Inside the mixing chamber tube 68 are mixing blades 82. Themixing blades 82 are stationary spiral blades which are set at rightangles to each other, as shown in FIG. 5, so that liquid travellingalong the path defined by the surface of one blade will be cut by thenext blade as the liquid flows past the mixing blades 82 through themixing chamber tube 68. Thus, the mixing blades 82, which are stationaryin the mixing chamber tube 68, provide a plurality of cutting edges 83,causing the gas bubbles to break up into very tiny bubbles. The mixingblades 82 are installed by pressing them between the two halves 66 ofthe mixing chamber when the halves are bonded together.

The mixing chamber is constructed so as to minimize the occurrence ofcrevices, cracks, porosity or small internal radii which could harborbacteria, and to facilitate in-place cleaning. All passages in themixing chamber slope back toward the pump 62, so that any liquid can bedrained during the cleaning process.

Sensors 49, 51 are located at the back of the mixing chamber near thetop to sense the pressure of the liquid/gas mixture as it leaves themixing chamber. These sensors indicate when to turn the pump 62 on andoff to maintain the pressure of the mix in the system. They alsoindicate when the pressure is much too low (i.e. due to a broken line)and cause the system to shut down in that event, turning on the "SystemFault" light on the control panel 25 in the process.

Looking now at the flow of fluids in the mixing chamber 42, as theliquid dessert mix is pumped into the bottom opening 74 of the mixingchamber 42, it enters a venturi section or small-diameter portion 70 ofthe mixing tube 68, the geometry of which imparts a high velocity to themix. At the small-diameter portion 70, the pressurized pure gas is alsointroduced through the opening 78. The gas and liquid then mix togetherin the static mixer, which is made up of the mixing chamber tube 68 withmixing blades 82 inside the tube. The mixing blades 82, confined by themixing chamber tube 68, form a tortuous path and a plurality of cuttingedges which break up the gas into tiny bubbles. The tortuous path is notthe zig-zag path of the mixing chamber tube 68 but rather the path theliquid inside the tube 68 must take in order to get past the blades 82.The purpose of the zig-zag path of the tube 68 is simply to get a longstretch of tube in a short vertical distance--not to cause the gas andliquid to mix. The amount of gas put into the mix is controlled bycontrolling the speed of the pump 62 which pumps the liquid mix and bycontrolling the pressure and flow rate of the gas coming from the bottle44. The pressure and flow rate of the gas are controlled by the pressureregulator 45 on the bottle 44 and by the adjustable needle valve 47 inthe gas line between the bottle 44 and the mixing chamber 42. Also, oneof the solenoid valves 46 turns the gas flow on and off. When thegas/liquid mixture leaves the mixing chamber 42 through the outlet 72,the air and liquid are very well-mixed. This reduces the need for mixingof the gas and liquid in the freezer 32. In tests which have beenconducted on this equipment, it has been found that the average bubblesize of the mixture coming out of the mixing chamber is under 100microns in diameter.

FIG. 6 shows the freezer 32 in more detail. The freezer 32 is made up ofa member 84, which has a substantially cylindrical inner surface 86 anda spiral groove in its outer surface 88. The member 84 is preferablycast, although it could be machined or made by other known methods. Atube 89 is shrunk over the outer surface 88 of the member 84 to create aspiral passageway for the refrigerant. This is accomplished by firstheating the tube 89 so that it expands and then slipping the expandedtube over the member 84 from back to front until it reaches the frontflange 91 of the casting 84. Then, when the tube 89 cools, it shrinksaround the casting 84 so that the refrigerant cannot slip through anyspace between the tube 89 and the casting 84 and must follow the spiralpath 88.

The assembled member 84 containing the spiral groove 88 together withthe outer tube 89 are then heated so that they expand, and then they areslipped over the inner core 94 until they abut the rear flange 96 of theinner core. There is an annular area 95 in which the member 84 has aninterference fit with the inner core 94. The diameter of the inner corein that annular area 95 is actually 0.003 inches larger than thediameter of the member 84 in that annular area when the member 84 andthe inner core 94 are at the same temperature, before the member 84 isheated and slipped over the inner core 94. When the member 84 and theinner core 94 cool off again, they are rigidly connected together withan interference fit, and there is no gap left between them to trapproduct. There are radiused corners 97 on the member 84 and the core 94just forward of the annular joint 95, again avoiding square corners orany place which could trap product.

The refrigerant enters the freezer 32 at the refrigerant inlet 90, atthe back of the freezer 32, passes through the spiral passageway 88, andleaves through the refrigerant outlet 92, near the front of the freezer32. This arrangement minimizes the expense in making the freezer andprovides for good heat transfer from the refrigerant to the product(avoiding problems of gaps between the coil which holds the refrigerantand the body of the freezer which are common in prior art designs),thereby improving the efficiency of the present evaporator over priorart evaporators. (It may be desirable to make the casting 84 out of amaterial which transfers heat well, which may not be a food-gradematerial, and to line the casting 84 with a food-grade material.)

The inner core 94 includes a rear flange 96, which abuts the rear wallof the member 84 and closes the back end of the freezer 32. The innercore 94 projects forward inside the member 84 almost to the front end ofthe freezer 32, creating a product chamber 98 in the space between theinner core 94 and the casting 84. The product chamber 98 has adoughnut-shaped cross-section (shown best in FIG. 7).

An outer tube 100 is fitted around the outside of the freezer 32,enclosing the rear flange 96 and the front flange 91 (the front flange91 being part of the casting 84), and forming an air space 101. Thecontrol air line 102 extends through that air space 101 and projects outthrough the front flange 91 to bring pressurized air to the rightdispenser 22, for controlling that dispenser, as will be describedlater. Two control air lines also extend through the front flange 91 ofthe left freezer 32 for controlling the left and center dispenser 18,20.

Behind each freezer 32 is a gear box 34, which has a drive shaft 104that projects inside the inner core 94 of the freezer 32 and is enclosedby the inner core 94. The drive shaft 104 is keyed to a coupling 106 ata first keyway 108, and the coupling 106 is then keyed to a second driveshaft 110 at a second keyway 112, so that, as the motor 36 drives thedrive shaft 104, it causes the second driveshaft 110 to rotate. Thesecond shaft 110 extends through rear and front bushings 114, 116, whichare press fit into the inner surface of the inner core 94. Thus, thedrive shafts 104, 110 collectively extend through the entire length ofthe inner core 94.

At the front end of the inner core 94 is a seal 118, which includes asubstantially toroidal body 119 that includes two O-ring seals 120 onits inner surface that seal against the second shaft 110 and one O-ringseal 122 or a sanitary seal/gasket on its back surface which is pressedbetween the seal flange 126 and the front face of the inner core 94 asthe seal 118 is threaded onto the inner core 94. Unlike prior artdesigns, in which the seal between the drive shaft and the freezer islocated at the back of the freezer, this seal 126, located at the frontof the freezer 32, is easy to remove and replace. To remove the seal126, the face plate 146 on the front of the freezer 32 must be removed,the dasher 132 is pulled out the front of the freezer 32, and then theseal 126 is rotated to unthread it from the core 94 and is removed outthe front of the machine. Once the seal 126 is removed, the second driveshaft 110 can then be pulled out the front of the freezer 32 to cleanout the inside of the core 94.

In prior art machines, if the seal at the back of the freezer leaks, theproduct goes out of the freezer into the back of the machine, where itcan accumulate. In this machine, if the seal 126 leaks, it will letproduct into the inside of the core 94. The product will follow thedriveshafts 110, 104 back to the back of the inner core 94 and will passdown through a gap 139 in the back of the freezer 32 which communicateswith the bottom of the inside of the core 94 and with an outlet opening141 which is connected to a tube (shown in FIG. 2) running to the frontof the machine, so that a leak would quickly be seen by the machineoperator as it drips onto the tray 26 at the front of the machine.

Having detected a leak, the machine operator would then run aclean-in-place cycle (which will be described later) to clean theproduct out of the freezer, open up the face plate 146, remove thedasher 132, the seal 126, and the second shaft 110, would clean out theinside of the core 94 and the drip tube running to the front of themachine, would replace the second shaft 110, put in a new seal 126,replace the dasher 132 and the face plate 146, and the freezer 32 wouldthen be ready to run again, with the leak having been promptly repaired.

The front-most portion 130 of the second shaft 110 has a hexagonalcross-section. The dasher 132 includes a front plate 134 with ahexagonal cross-section hole 136 in its center, which fits onto thehexagonal end 130 of the second shaft 110 so that the dasher 132 can bedriven by the motor 36. The rest of the dasher projects back into theproduct chamber 98 to scrape the product which sticks to the cylindricalsurface 86 of the casting 84 as the liquid mix freezes and to mix theproduct and move the product forward toward the dispensers. The dasher132 is shown in more detail in FIG. 8.

The dasher 132 has a very different shape from prior art dashers,because it has to have an opening at one end which leads to a hollowcenter portion that fits over the core 94 of the freezer 32. In thepresent invention, because of the small bubble size of the aeratedliquid entering the freezer 32, the dasher 132 does not have to do asmuch mixing and can operate at a much slower speed than do the dashersof the prior art. The dasher of the present invention preferably rotatesin the range of 25-50 rpm (most preferably about 35 rpm), as comparedwith speeds of 100 rpm or greater in the prior art. This saves energy,because it requires less work to rotate the dasher at a slower speed.

There is a product inlet 138 at the bottom and back of the freezer 32,which permits the aerated liquid mix to enter the back of the productchamber 98. In order to avoid the problem of the product inlet 138freezing up and plugging, there is an inlet heater 140 surrounding theinlet 138. As is shown in more detail in FIG. 7, the inlet heater 140includes a tube 142 which carries refrigerant to a chamber 144, whichsurrounds the product inlet 138. The refrigerant which goes through thetube 142 and the chamber 144 is at the point in the refrigeration cyclebefore it has been expanded, causing its temperature to drop. It is notso warm that it would warm up the product as it enters the freezer 32,but it is warm enough to prevent the product from freezing up at theinlet and plugging the inlet. As the product moves from the inlet 138 atthe back of the freezer 32 toward the front of the freezer 32, theproduct is frozen. The dasher 132 scrapes the product off of the innersurface 86 of the casting 84 and propels the product toward the front ofthe freezer 32. The product inside the freezer 32 is under pressure, dueto the pump 62, so that, when a dispenser opens, the product willautomatically move to the low pressure outside the dispenser.

As shown in FIG. 6, at the front of the freezer 32 is a face plate 146which is bolted to the front of the casting 84 and is sealed against thefront face of the casting 84 by means of O-ring seals 148 and 150 orsanitary seals/gaskets. The large O-ring 148 seals around the productchamber 98, and the small O-ring 150 seals around the control airopening 152, which brings the control air to the dispenser. The controlair enters the dispenser chamber at the opening 153. As shown in FIG. 9,the face plate 146 has nine openings toward the casting 84--three topopenings 154 for receiving pressurized air to control the threedispensers, four bottom openings 155 for letting frozen dessert into thedispensers (one bottom opening for each of the left and right dispensers18, 22 and two bottom openings for the center dispenser 20, whichdispenses from both freezers 32), and two openings 182 leading from thetop of the two product chambers 98 to the vent lines 187, for ventingair out of the freezers 32 as they are initially filled with product orwith cleaning fluid. One of the top openings and one of the bottomopenings are shown in FIG. 6. The top opening 154 is aligned with thecontrol air opening 152 in the casting 84, and the bottom opening 155opens into the bottom of the product chamber 98 so as to receive productfrom the freezer 32. The other openings are shown in FIGS. 9 and 10,which will be discussed later. There is a bore 156 in the face plate146, which receives a bushing 158 that supports the end of the secondshaft 110 so the shaft 110 does not float axially as it rotates.

FIG. 6 shows the right dispenser 22. The left and center dispensers 18,20 are identical to the right dispenser 22, except that the centerdispenser 20 receives product from both freezers 32. The dispenser 22includes a plunger 160, which is biased downward by means of a helicalspring 162. The helical spring 162 lies in the plunger chamber 164 andabuts the top surface of the plunger 160. The plunger 160 is sealedagainst the cylindrical inner wall of the plunger chamber 164 by meansof an O-ring 166 and is attached to a plunger shaft 168, which extendsdown into a smaller diameter dispenser tube 170, which terminates at thedispenser opening 172, where the product leaves the machine 10. Theplunger shaft 168 is sealed against the smaller diameter dispenser tube170 by means of O-rings 174.

When the plunger 160 is in the resting position, biased downward by thespring 162, the O-rings 174 on the plunger shaft 168 which arepositioned above and below the bottom opening 155, prevent the productfrom leaving the freezer 32. When a button 24 is pushed, telling thecentral processor that the operator wants to dispense frozen dessertfrom that dispenser, control air from the control air system entersthrough aligned openings 152 and 154 into the upper portion of thedispensing tube 170 and pushes against the bottom surface of the plunger160, causing the plunger 160 to move up until the plunger shaft 168 andO-rings 174 lie above the product opening 155. This allows product toflow out of the freezer 32, into the dispenser tube 170, and out of themachine 10 through the dispenser opening 172. When one of the solenoidvalves 46 vents the control air, air pressure is removed from theplunger 160. The dispenser valve 22 then closes again due to the biasingaction of the spring 162, so that no more product is dispensed. Theproduct sits in the product chamber 98 of the freezer until the machineoperator again pushes a button 24, sending a signal to the centralcontroller to send control air to the dispenser valve again. The motor36 continues to run, whether or not product is being dispensed, but theflow of refrigerant to the freezer 38 is turned on and off based on theviscosity of the product in the freezer (which is measured by measuringthe amperage drawn by the motor 64). The pump 62 is turned on asnecessary to maintain the product pressure, sensed by the sensor 49, aswas explained earlier. The control of the dispensers will be describedin more detail in the description of FIG. 11.

FIGS. 7 and 8 show the dasher 132, including scraper blades 133, whichscrape frozen dessert off of the wall 86 of the freezer 32, and angledblades 135, which mix the frozen dessert and propel it toward the frontof the freezer 32.

FIGS. 9 and 10 show the dispensers 18, 20, 22 and the associated flowpaths, inlets and outlets. The left and right dispensers 18, 22 functionas described above. The center dispenser 20 functions in essentially thesame way, except that it receives frozen dessert from both the left andright freezers 32 along the paths 176, 178. The control air line whichcontrols the center dispenser 20 runs in the air space 101 of the leftfreezer 32.

It should also be noted that there is an additional plunger 180associated with each of the left and right dispensers 18, 22 (not withthe center dispenser 20). These additional plungers 180 are manuallycontrolled and are for the purpose of purging air from the freezers 32when the freezers are initially filled with mix or when the freezers arecleaned in place (whenever it is necessary to purge air or gas from thefreezer 32 in order to fill it with liquid). The plungers 180 each havea stem 181, provided with a pair of spaced O-rings 183 abutting the wallof the plunger chamber 185. Each plunger chamber 185 includes an opening189 to a passageway 187, which leads to the top of the product chamber98 of the respective freezer 32. When a plunger 180 is in the restingposition, its O-rings 183 lie above and below that opening 189, closingit off. When a plunger 180 is manually lifted up, the O-rings 183 lieabove the opening 189, permitting air or other fluid from the productchamber 98 to be vented out the bottom opening 191 of the plungerchamber 185.

Unlike other soft-serve frozen dessert machines, which must be takencompletely apart, the pieces washed, and then reassembled every day, themachine of the present invention can be cleaned in place because it doesnot have cracks or crevices that can harbor stagnant product. In orderto clean the machine 10 in place, the following procedure is followed.

CLEAN-IN-PLACE PROCEDURE

First, the person operating the machine pushes the off button, which isone of the buttons on the panel 25. This turns off the system, includingthe refrigeration unit and the pump 62. To keep from damaging the dasherdue to highly viscous product, the dasher remains on and is turned offonly after the first clean cycle has been completed. Then, the persondisconnects the product boxes 40 from their valving 60, and connects thevalving 60 to a rinse solution. The rinse solution may be in a bucket,in which case the valving 60 is submerged in the bucket, or it may be ina box identical to the product boxes 40, in which case the valves 60would be connected to the rinse boxes in the same way as they wereconnected to the product boxes 40.

The respective dispensing heads 18, 20, 22 may be connected to dischargehoses leading to a sink or drain, or a bucket may be put under thedispensing heads 18, 20, 22 to catch the rinse solution which comes outof the dispensing heads. The operator then pushes the "clean" button onthe control panel 25 (again, there is a separate control panel 25 foreach freezer 32, so the operator may be pushing the "clean" buttons onboth panels 25 to clean both freezers at the same time). The "clean"button communicates with the central processor 186, which then runs themachine through a timed cycle. At the beginning of the clean cycle, the"clean" button is pressed, and the central processor then initiates theproduct pump-out sequence. In this sequence, the pump operates in thereverse direction for a certain time period, during which all liquidproduct is pumped back into the box 40. Also, during this sequence, therespective dispensing head 18 or 22 must be opened to allow the icecream to be pumped out (so the pump is not trying to pull a vacuum).Then, the vent valves 180 must be manually lifted up to permit the gasin the freezers 32 to escape until the freezers 32 fill up with rinsesolution. Then the vent valves 180 are closed.

The timed cycle runs the pumps 62 and the motors 36, running the rinsesolution through the entire path that the product takes, from thevalving 60 through to the dispensers 18, 20, 22. The timed cycleincludes opening and closing the dispenser valves 18, 20, 22 so thatrinse solution goes through the entire system. Then, the pumps 62 run inreverse to drain the rinse solution out of the machine. Then a light onthe "clean" button flashes to tell the operator that it is time to startthe next part of the cleaning process.

Next, the rinse solution is disconnected from the valves 60 and isreplaced with cleaning solution, the "clean" buttons are pushed again,starting the second cleaning cycle. The vent valves 180 are lifted untilthe freezers fill up, and the central processor goes through the sameprocedure as was used with the rinse solution but with cleaningsolution. The cleaning solution is agitated in the freezer 32, goes outthe dispensers, and, at the end of the timed cycle, the pump 62 isreversed, to drain cleaning solution out of the machine. Then, the"clean" light flashes again.

Next, the cleaning solution is disconnected from the valves 60, and asanitizing solution is connected to the valves 60. The "clean" button orbuttons are pushed again, starting the sanitizer part of the cleaningcycle, and the vent valves 180 lifted up again until sanitizing solutionsquirts out the openings 191, at which point the vent valves 180 areclosed again, and the timed sequence repeats, turning the pump on andoff, opening and closing the dispenser valves, agitating the sanitizingsolution with the damper, and so forth, until the sanitizing solution ispumped back out. Again, the "clean" light flashes, telling the operatorthat another step must be taken.

Next, the operator disconnects the sanitizing solution, connects a coldwater rinse, pushes the "clean" button again and the machine then goesthrough the whole timed sequence again. At the end of this finalsequence, the "clean" light goes out.

Now, the product path is clean. The machine may be stored at this point,or it may be reconnected to product boxes 40. The connectors 60 shouldbe dipped into sanitizer solution prior to being connected to newproduct. The "on" button must be pushed to start the machine up again.

Since the liquid mix is kept refrigerated at all times and is connectedaseptically to the machine 10, and since the gas that is mixed with theliquid mix is pure, uncontaminated gas, the product is very clean andcan stay in the machine for a much longer period of time than can priorart soft-serve machines before any bacteria begins to build up in theproduct. Therefore, it is anticipated that these machines will be ableto operate for a much longer time than prior art machines before theyneed to be cleaned. When they do need to be cleaned, the cleaning is avery simple process, as described above, which does not requiredisassembly of the machine. This will save a tremendous amount of laborand will ensure that the machines actually are cleaned as they should bein order to maintain a clean product.

FIG. 11 is a schematic diagram showing the control for the dispensers18, 20, 22. The control panel on the front of the machine includes thethree sets of dispenser control buttons 24 and two sets of machinecontrol buttons 25. The sensors 184 are connected to their respectivedrive motors 36, which drive the dashers in the freezers. The sensors184 sense the amount of current that is drawn by the motors 36 as theydrive the dashers 132. The amount of current drawn by the motorscorresponds to the viscosity of the product in the freezer, so, when theproduct becomes very viscous and it is difficult to drive the dasher,the current draw increases, and the sensor 184 tells the centralprocessor 186 that it should close the solenoid valve which controls theflow of refrigerant to that freezer. If the solenoid valves to bothfreezers are closed, the central processor 186 will stop the condensingunit. When the product begins to thaw and become less viscous, thecurrent draw drops back down, and the sensors 184 tell the centralprocessor 186 to open in the refrigerant solenoid valve and start thecondensing unit if it is not already on. The dispensing heads 18, 20, 22dispense frozen dessert from the machine. The central, programmablecontroller 186 controls the dispensing of the frozen dessert from thedispensing heads. The compressor and air tank 50 provide the workingfluid for controlling the dispensers. Among the solenoid valves 46 areair valves 188, which provide the compressed air to the dispensingvalves 18, 20, 22 and vent air from the dispensing valves 18, 20, 22 tocontrol the dispensing of the frozen dessert.

When the machine operator wants to dispense product from one of thedispensers 18, 20, 22, the operator pushes one of the buttons 24. Whenthe controller 186 receives a signal from one of the buttons 24, itknows which dispenser to open and how long to hold the dispenser open inorder to dispense the desired amount. Then, the controller 186 causesthe appropriate air valve 188 to open, allowing pressurized working airfrom the compressor and tank to flow into a particular dispenser,causing that dispenser to open. The controller will keep the dispenseropen for a preset period of time and will then close the air valve 188and allow the pressurized air in the dispenser to be vented, therebyclosing the dispensing valve. The portion size for any given button 24can easily be reprogrammed by the machine operator by holding thecontinuous flow button and the small, medium or large button for thedesired amount of time. That new time will be put in memory and will notchange until the operator repeats that procedure. This permits theoperator to have tight control over the portion size for any givenfrozen dessert product.

The dispenser buttons 24 are labelled "small", "medium", "large", and"flow". The small, medium and large are programmed portion sizes, and"flow" is a continuous flow button, which might be used to fill a verylarge container with product, for example. The continuous flow buttonholds open the dispensing head as long as it is depressed. It is alsoused to program the other buttons as described above.

Some of the machine control buttons 25 have already been described. The"low product" light comes on when the switching valve 41 switches fromone box of mix 40 to another, telling the operator that one box of mix40 is empty and must be replaced. When the operator replaces the box 40,he pushes the reset button to turn off the "low product" light.

When the pressure sensor on the bottled gas senses a drop in pressure inthe bottle, it communicates with the central controller 186, which turnson the "low product air" light. The operator then switches the machineover to the other bottle of gas, and the pressure switch is resetbecause of adequate pressure from the new bottle.

If the product temperature in the refrigerated compartment gets toohigh, the product temperature light will come on, shutting the machinedown and requiring maintenance. If a hose breaks or some other problemoccurs, causing a pressure drop, the "system fault" light will come on,shutting the machine down and requiring maintenance.

In a second embodiment of the invention, shown in FIG. 12, the freezer32 is essentially the same as the freezer shown in FIG. 6, except thatrefrigerant also circulates in a coil 190 in the inner core 94, creatingan inner heat transfer surface 192 in the product chamber 98 of thefreezer 32.

It will be obvious to those skilled in the art that the machinedescribed above may be modified without departing from the scope of thepresent invention.

What is claimed is:
 1. In a frozen dessert machine, including a freezingchamber having an outer heat transfer wall; a liquid inlet port in saidfreezing chamber; a dispenser port at the front of said freezing chamberfor dispensing the frozen dessert from the freezing chamber; said inletand dispenser ports being separate from each other such ttmt liquid mayenter through the inlet port as product leaves through the dispenserport; a dasher for mixing the frozen dessert in the freezing chamber andfor scraping tile frozen dessert off the outer heat transfer wall of thefreezing chamber; and including a drive at tile back of said freezingchamber for driving said dasher; characterized in that:said freezingchamber further includes an inner core extending from the back of thefreezing chamber toward the front; a drive shaft extending from saiddrive at the back of said freezing chamber and connected to said dashernear the front of said freezing chamber; said drive shaft being enclosedby said inner core.
 2. In a frozen dessert machine as recited in claim1, and further comprising:a seal located at the front of said freezingchamber for sealing between said drive shaft and said freezing chamber.3. In a frozen dessert machine as recited in claim 2, wherein said sealincludes a substantially toroidal body, having an inner surface, anouter surface and front and back surfaces, and including a seal on itsinner surface for sealing against the drive shaft and another seal onone of its surfaces for sealing against the inner core of the freezingchamber.
 4. In a frozen dessert machine as recited in claim 3, whereinsaid toroidal body includes threads for threading the toroidal body ontothe inner core.
 5. In a frozen dessert machine as recited in claim 1,wherein refrigerant circulates in said inner core, creating an innerheat transfer surface in said freezing chamber.
 6. In a frozen dessertmachine as recited in claim 1, wherein said inner core is substantiallycylindrical.
 7. In a frozen dessert machine, including a freezingchamber having an outer heat transfer wall; a liquid inlet port in saidfreezing chamber; a dispenser port at the front of said freezing chamberfor dispensing the frozen dessert from the freezing chamber; said inletand dispenser ports being separate from each other such that liquid mayenter through the inlet port as product leaves through the dispenserport; a dasher for mixing the frozen dessert in the freezing chamber andfor scraping the frozen dessert off the outer heat transfer wall of thefreezing chamber; and including a drive at the back of said freezingchamber for driving said dasher; characterized in that:said freezingchamber includes an inner core spaced from said outer heat transfer wallover substantially its entire length and extending substantially thelength of said chamber; a drive shaft enclosed by said inner core andoperatively connected to said drive at one end and to said dasher at theother end.
 8. A frozen dessert machine as recited in claim 7 in whichone end of said inner core abuts said outer heat transfer wall.
 9. Afrozen dessert machine as recited in claim 7, wherein said outer heattransfer wall is formed from a member which, on its outer surface,defines a groove, which is enclosed by a tubular member to form a spiralpath so as to receive refrigerant.
 10. A frozen dessert machine asrecited in claim 7, and further comprising:a mixing chamber upstream ofsaid freezing chamber, said mixing chamber including a liquid inlet forreceiving liquid frozen dessert mix; a gas inlet downstream of saidliquid inlet for receiving gas to be mixed with the liquid; a tortuouspath downstream of said gas inlet for mixing the gas and liquidtogether, breaking the gas into tiny bubbles; and a product outlet influid communication with the product inlet of the freezing chamber, sothat the mixed gas/liquid product leaving the mixing chamber can enterthe freezing chamber.
 11. A frozen dessert machine as recited in claim10, and further comprising a pump in fluid communication with saidliquid inlet for pumping liquid into the mixing chamber.
 12. A frozendessert machine as recited in claim 11, and further comprising:asmall-diameter area in said mixing chamber in the area of said gasinlet, so as to increase the velocity of the liquid at the point wherethe gas is introduced.
 13. A frozen dessert machine as recited in claim12, and further comprising a bottle of pressurized gas in fluidcommunication with said gas inlet.
 14. A frozen dessert machine asrecited in claim 10, wherein said dispenser is fluid-operated.
 15. Afrozen dessert machine as recited in claim 12, wherein said dispenser isfluid-operated.
 16. A frozen dessert machine as recited in claim 12,wherein the machine defines a product path from the liquid inlet of themixing chamber to the dispenser which slopes toward the liquid inlet atall times, to facilitate drainage of fluids out of the machine forcleaning.
 17. A frozen dessert machine as recited in claim 16, whereinthe product path from the liquid inlet of the mixing chamber to thedispenser is a smooth path suitable for clean-in-place procedures.
 18. Afrozen dessert machine as recited in claim 7, and further comprising aleak detection tube from the inside of the inner core to the front ofthe machine, such that, if product leaks into the inner core, it willpass through the tube to the front of the machine, so it can be readilydetected by the operator.